One installation of solar module is to install the solar module onto the surface provided by a rack system on a roof or ground. The process of the traditional installation of solar module comprises:                1. Screwing anchorages on the roof (or if ground mounted, stick pillars in the ground or concrete);        2. Sealing the holes on the roof at the anchorage points;        3. Assembling a rack system made by rigid and heavy parts;        4. Securing the rack system to the anchorage points on the roof or on the ground;        5. Screwing the solar modules on the rack;        6. Electrically connecting solar modules with electric cables.        
A traditional variant of screwing rack system into the roof is to make the whole system heavier with ballasts.
However, roofs are often designed to support a limited static load and this is not enough to support the gravity of solar modules and mounting system.
Each contact point of rack and roof needs a mounting hole which damages the membrane and may damage the roof. And each hole needs to be sealed which will increase costs for labor, material and roof insurance.
Professional labor is necessary to assemble the framework, to screw the modules to the framework, and to connect electric wires.
The framework for supporting the modules leads to expensive costs for material and transport.
Japanese patent JP200-71805 discloses a cable structure consisting of cable net which is weaved by longitudinal cables and latitudinal cables. The grid of the cable net provides a space in which a solar module is placed. The four sides of the solar module are respectively supported by the four sides of one grid. And the cable net is placed on a slope provided by a rigid rack. Such cable structure needs many cables, and cables are very expensive: thus, it is very hard to decrease the cost of the cable structure. Except that, the rack is also necessary, and accordingly the rack must be screwed or ballasted on the roof.